MadSci Network: Engineering


Date: Thu Nov 15 12:04:52 2007
Posted By: Donald Howard, Nuclear Engineering, Retired
Area of science: Engineering
ID: 1195090023.Eg

In many of the older installations, when someone decided that it would be 
convenient to have 3-prong outlets, they just installed them the way yours 
is wired.  I doubt that’s code, but as far as safe is concerned, if you 
didn’t do it yourself, then one of the previous owner did it or had it 
done a long time ago.  

As far as safe goes, there’s a debate about how safe is safe.  Originally, 
there was no ground wire.  Then folks found that if they were using, say, 
a mixer on the sink counter and touched both it and the water faucet, 
which was grounded, it made their hand feel like their foot was asleep 
only stronger.  The next step up was what you are seeing – to install a 
ground and tie one side of a single phase circuit to it – aka, the neutral 
or left pin on a 3-prong outlet or the left or wide slot on a two pronger. 

Works well and has for decades except under some weird conditions like 
lightening strikes and strange things that may happen in the bathroom that 
has caused the codes to require a Ground-Fault-Interrupter in outlets 
around water – bathroom sink and laundry rooms.  You can tell those by the 
TEST button in the middle of the outlet. 

Without seeing it, I’d bet that every outlet in your house is wired that 
way and has been for a long time.  Technically, it works.  Codewise, I’d 
have to check your local requirements, and if worrying about it is causing 
you to lose sleep, get a second opinion from a local contractor.  But, be 
aware that the contractor most probably will recommend additional wiring 
to bring things up to code, which is something you may have to do anyway 
if you want to sell the place.

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